1. Field of the Invention
The invention relates to a charging control method, and more particularly, to a method for charging a power device of a portable device using a current-adaptive process according to the capability of a charger.
2. Description of the Prior Art
Portable devices like tablet computers, mobile phones, or power banks, are charged commonly in constant voltage and constant current. With the increase of battery capacity of portable devices, the bundled charger also has larger specified charging current. It is very common to have many chargers in hand, some with large specified current like 1500 mA, 2000 mA or even more, and others with small specified current like 1000 mA or less. Besides charging the corresponding tablet computer or mobile phone, people can pick one charger and connect it to other portable devices for charging the device, thanks to the fact that these chargers may share the same connector specification.
It is also a known fact that the power device of each different portable device should be charged with no more than its acceptable maximum charging current and each charger also has its capability to provide some maximum charging current. When the power device is being charged, it draws as much current as it can take from the charger to the limit the charger can provide and when the charger is capable of affording a maximum charging current that is no less than what the power device can take, the charger is quite qualified to charge the power device via the maximum charging current the power device can accept. However, if the charger can provide no more than what the power device can take, i.e., the power device is being charged by the charger with insufficient specified current output (for example, the power device may be charged with as much as 2 A while the charger can only afford a charging current up to 1 A), it maybe the case that the power device will continuously try to draw current higher than what the charger can afford from the charger. This may cause the charger to activate a protection mechanism to stop providing power intermittently. Under some circumstances, the charger may even be force to provide too much current beyond its designed capability for the power device, and it should do harm to the charger in the long run, since excessive current provision by the charger has gone out of range of the safety regulation for designing the hardware and the wiring of the charger.